Multiple wavelength fluorescence enhancement on glass substrates for biochip and cell analyses.

In microarrays experiments, a serious limitation is the unreliability of low signal intensities data and the lack of reproducibility for the resulting ratios between samples and controls. Most of the light emitted by a fluorophore at the air/glass interface of a glass slide is absorbed by the glass so just a part of the emitted fluorescence is detected. To improve the sensitivity of the fluorescence detection of both common fluorophores Cy3 and Cy5 in DNA microarrays and fluorescent cell analyses, we have designed a multi layer mirror with alternative thin layers of SiO2 and HfO2. This mirror (MOTL) prevents fluorescence absorption, allows the simultaneous enhancement of the fluorescence signals and increases the dynamic range of the slides. Using MOTL slides, Cy3 and Cy5 intensities are enhanced by 5-8-fold, consequently, the fluorescence analysis becomes easier and should allow the detection of low copy number genes or weakly fluorescent cells. With the same approach, other multiple optical thin layer slides could be designed for other series of fluorophores, extending the field of their applications.

Toxicity and bioaccumulation of fipronil in the nontarget arthropodan fauna associated with subalpine mosquito breeding sites.

In order to examine ecological impact of fipronil use for larval culicine control in natural hydrosystems, toxicity and bioaccumulation of this new insecticide were analyzed on aquatic species representative of the nontarget arthropodan fauna (nonculicine larval Diptera: Chaoboridae, Chironomidae; planktonic Crustacea: Cladocera, Copepoda, Ostracoda) associated with target larval mosquito populations in the subalpine breeding sites. Standard toxicological bioassays using fipronil aqueous solutions from 1 to 2000 nM indicated different sensitivity levels among species. Insecticide bioaccumulation analyses, using [(14)C]fipronil solutions in simplified laboratory ecosystem, also indicated large differences among species. These differences may come from biological parameters characteristic of each species. Taking into account these nontarget effects of fipronil, a possible strategy of use of this insecticide for integrated mosquito control management was proposed, which is based upon selective dietary absorption of the insecticide by larval Culicidae.

Infrared ellipsometry investigation of SiO(x)N(y) thin films on silicon.

The dielectric function ˜ε (˜ε = ε(1) + iε(2)) of silicon oxynitride films deposited on silicon wafers by dual ion-beam sputtering is determined by infrared ellipsometry between 580 and 5000 cm(-1). The phase-separation model is unable to reproduce the experimental data. The dependence of ˜ε on stoichiometry is analyzed with the microscopic Si-centered tetrahedron model. The random-bonding model with five SiO(4-j)N(j) (j = 0-4) tetrahedra gives a good description of the spectra, provided the dielectric function of the mixed tetrahedra is carefully chosen.

Determination of refractive-index profiles by a combination of visible and infrared ellipsometry measurements.

Model inhomogeneous silicon oxynitride films were produced by ion-beam sputtering and characterized by ellipsometry in the visible and infrared ranges. These films exhibit strong intentional gradients of the refractive index that cannot be considered linear. A discrete description of the index profile with a few layers or a continuous description with a polynomial are examined; regressions by the use of measurements in the visible only or in the total spectral range (visible and infrared) are performed. Acquisition of data in an extended range is found to be a guarantee of the reliability of the calculated index profiles.

Thin-film designs by simulated annealing.

With the increasing power of computers, new methods in synthesis of optical multilayer systems have appeared. Among these, the simulated-annealing algorithm has proved its efficiency in several fields of physics. We propose to show its performances in the field of optical multilayer systems through different filter designs.